Harrison's PodClass: Internal Medicine Cases and Board Prep Ep 172: A 52-Year-Old Man with an Increased Respiratory Rate
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Nov 13, 2025 A clinical case about a middle-aged man with progressive hyperventilation leads into a deep dive on metabolic acidosis and interpreting ABGs. They explore causes of normal anion gap acidosis, urine anion gap interpretation, and distinguishing renal tubular acidosis subtypes. The discussion connects diabetes, hyperkalemia, and diabetic nephropathy to type 4 renal tubular acidosis.
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Patient Compares Current Breathing To Prior DKA
- The patient felt the need to hyperventilate at rest and recalled a prior DKA episode with similar breathing.
- Charlie Wiener and Cathy Handy Marshall used that history to prompt an urgent ABG.
PCO2 Rule Of Thumb For pH
- An acute drop in PCO2 raises pH by ~0.08 per 10 mmHg, helping distinguish acute vs chronic acid-base disorders.
- Cathy Handy Marshall uses this bedside rule to estimate how much respiratory compensation masks metabolic acidosis.
Calculate The Anion Gap First
- Always calculate the serum anion gap as the next step when you find a metabolic acidosis.
- Charlie Wiener emphasizes this to distinguish anion-gap from non–anion-gap causes quickly.
